1. Field
The present invention relates to a method and system to diagnose exhaust gas sensor deterioration.
2. Description of the Related Art
A conventional automobile includes an engine which combusts a mixture to generate an exhaust. The composition of the exhaust is regulated by governmental agencies for pollutants. To reduce the amount of pollutants, the air-fuel ratio of the mixture can be controlled. The conventional automobile utilizes an exhaust gas sensor to determine air-fuel ratio data for an exhaust of an engine. Such air-fuel ratio data can determine adjustments to the air-fuel ratio of a mixture supplied to the engine. Such adjustments, however, can be incorrect when the exhaust gas sensor malfunctions due to deterioration.
Conventional methods to detect exhaust gas sensor malfunctions have utilized threshold switching based on the air-fuel ratio data. However, such methods cannot use fixed gain and fixed frequency because the air-fuel ratio data may not cross the necessary thresholds as the sensor response slows.
Furthermore, governmental agencies are increasingly demanding that malfunctions be detected not just for the overall operations of the exhaust gas sensor, but in a more finite manner, such as during lean to rich fuel operations or rich to lean fuel operations. Conventional methods, however, are unable to parse the malfunctions in such a manner.
In addition, conventional methods generally require that the automobile be at a constant speed for a large number of cycles, such as 12 output cycles. With the large number of cycles, there is an increased chance that the method will be interrupted due to a change in automobile speed. This reduces the amount of tests that can be performed and/or increases the number of attempts that must be made in order to diagnose the exhaust gas sensor deterioration, both of which are undesirable.
Thus, there is a need for a method and system to diagnose exhaust gas sensor deterioration.